The Model-View-Controller (MVC) pattern separates an application into three components:

• Model - maintains the state of the program, contains the data store
• View - creates a 'view', that is it transforms the model data into a form accessible to the user
• Controller - implements a user interface that allows the user to interact with the model

The MVC pattern is an updated version of the old adage that computer programs come in three parts: input, processing, and output. It is a nice way to describe the high-level architecture of an application because Views and Models naturally separate form from content. Separating form from content usually leads to cleaner code and greater flexibility.

For a future web application, I am meditating on the best approach to take for the view and model. There are two general approaches I am looking at.

The first is a traditional perl templating scheme. The model would be a flat file or relational database, bound to a perl program through DBI. The view would consist of a set of template documents that would transform data to various formats (HTML, plain text, CSV, etc.) using, for example, Template::Toolkit.

The second approach is to build an XML application. The model stores data in an XML format and is accessed directly, or perhaps using XML::LibXML. The view would consist of a set of template documents that would transform data to various formats (HTML, plain text, CSV, etc.) using the XSLT language via, e.g., XML::LibXSLT.

I have little experience with either templating scheme, and I am seeking advice on the pros and cons of these two approaches. I understand that the subject of XML vs. relational databases is contentious. Let's assume that I am comfortable implementing either variety. and that the database will be small enough that performance considerations will not be foremost in the design. Also, if performance becomes a problem, I could create an XML wrapper around DBI results. So the comparison becomes that of a perl templating language vs. XSLT.

Some questions pertaining to the comparison are

• I'd like the code to be maintainable after I leave. Is it reasonable to expect novice programmers to be able to learn to manipulate and modify Template Toolkit templates? What about XSLT?
• XSLT seems like a cool language in theory, but how is it in practice? Does it DWIM, or is it fussy and frustrating?
• One aspect of XML/XSLT I like is that they are language neutral. Once the docs and templates are written, they can be processed in any number of languages: Perl, Java, C, C++, Python, etc. On the other hand, Perl and associated templating systems are in widespread use and not going away any time soon, so perhaps language neutrality is not so important?
• Associated with XSLT is XSL-FO, an XML formatting language. Is XSL-FO commonly used as part of the transformation process?

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